1. Field of the Invention
The invention pertains to the field of electronically scanned antennas and more particularly to commutation switches for electronically scanned cylindrical arrays.
2. Description of the Prior Art
A cylindrical array comprises a multiplicity of individual radiating elements arranged in columns and rings. In such an array, a directive antenna beam is formed by simultaneously exciting the columns with an amplitude and phase distribution (illumination function) that produces the desired antenna pattern. This beam may be electronically scanned about the cylinder axis by commuting the illumination function around the columns of the cylindrical array with the utilization of electronic switching circuits.
A binary commutation switch for commuting the illumination function around the columns of the cylindrical array, thereby scanning the antenna about the axis of the cylinder, is disclosed by Giannini in U.S. Pat. No. 3,816,830. In accordance with the Giannini disclosure a multiplicity of 2.times.2 transfer switches form a N.times.N commutation switch, where N=2.sup.n and n is an integer. The total number of 2.times.2 switches in the N.times.N commutation switch is Nn/2. Single pole-two-throw (SP2T) and single-pole-three-throw (SP3T) switches may be coupled to each output port of the N.times.N commutation switch to respectively scan cylindrical array antennas with 2N and 3N columns. In general, SPMT switches may be added to the N.times.N commutation switch to scan a cylindrical array of MN columns, where M is the number of antenna columns switchably coupled to each output port of the commutation switch.
Utilization of the Giannini commutation switch in large cylindrical arrays requires a significant number of transfer switches, appreciably adding to cost of the array. A commutation switch which provides an appreciable reduction in the number of transfer switches is therefore desirable.